ASoC: Make the DAI ops constant in the DAI structure

Neither drivers nor the core should be fiddling with the actual ops
structure at runtime.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

include/sound/soc-dai.h

@@ -203,7 +203,7 @@ struct snd_soc_dai_driver {
 	int (*resume)(struct snd_soc_dai *dai);
 
 	/* ops */
-	struct snd_soc_dai_ops *ops;
+	const struct snd_soc_dai_ops *ops;
 
 	/* DAI capabilities */
 	struct snd_soc_pcm_stream capture;